shared_ptr's and sets

From: radelber_at_[hidden]
Date: 2000-12-13 11:40:58

Forgive me if this is the wrong place. I have a question concerning 
implementation rather than semantics.

I have a need for a simple database that stores one copy of an 
object. If an object being inserted already exists, a pointer to it 
is returned. If the use_count drops to zero the object should be 
deleted.

I'm thinking of using a set of shared_ptr. Is this a good solution?

I have a class, myEvent
typedef shared_ptr < myEvent >     EventPtr;
typedef EventPtr::iterator         EventIter;

set<EventPtr>   EventDb;   // my database

MyEvent* pQuery = new MyEvent(...)  // create new entry
EventPtr cp(pQuery)                 // create shared_ptr
                                    // insert the object
pair<EventIter, bool> pair1 = EventDb.insert(cp);
cp = *pair1.first;

1. Is this correct? Reguardless of pair1.second, the original value 
of cp (pQuery) is destroyed and cp points to either the newly 
inserted (pQuery), or a previous shared_ptr.

1b. Or if I reassign cp, does the inserted pQuery end up being 
destroyed?

2. How do I know when to delete the cp from the set? the shared_ptr 
will delete the object it points to, but do I have to check if 
use_count < 1?

3. Does the constant creation of new objects and deletions at insert 
time cause memory fragmentation problems?

Thanks in advance,

Rob

Rob Adelberg     radelber_at_[hidden]
Arinc, Inc.